Studies on microalgal strain improvement for enhanced biodiesel production by use of genetic engineering

Abstract

Recently, biodiesel has gained increasing attention as the substitute for petrole-um-based fuels. Microalgae have been considered as an alternative feedstock for biodiesel due to their ability such as high lipid contents and rapid growth. However, it is necessary to fur-ther develop microalgal strains by understanding the genes controlling lipid accumulation in microalgae for enhanced biodiesel production. The main objective of present study is the im-provement of microalgal strains for improved lipid production by using random mutagenesis and targeted genetic manipulation. In this study, the mutant strains, CR12 and CR48, were generated by random muta-genesis of Chlamydomonas reinhardtii wild-type. CR12 strain displayed the phenotype of in-creased lipid content as lipid while CR48 had decreased lipid content compared to the wild type strain of C. reinhardtii. To gain molecular insights on the phenotypes of the mutant strains, a proteomics analysis was conducted to investigate the differences in the patterns of protein expression between mutants and wild type strains. Based on the result from prote-omics study, the proteins up- or down-regulated at least 2-fold either in wild-type or CR12 or CR48 were identified. Our results indicate a possibility of identifying additional genes that might belong to other pathways that are not directly linked to the lipid biosynthesis in micro-algae.Additionally, we attempted to understand signaling pathways behind lipid biosynthe-sis. MAP kinase plays a decisive role in intracellular signaling transduction and has an influ-ence on the control of processes such as differentiation, stress reactions, development, and apoptosis. In this study, repression of MAP kinase gene expression using RNA interference resulted in increased level of lipid content in microalgae.